+ added errors on track parameters
+ added option to use vertex constraint for circles
+ for allowed distance between hit and track different values can be used before and after the fit
+ for circles use inverse of distance between origin and center of circle instead of the distance
Interfaces changed.

- fixed bug in TrackerHitPlaneImpl and TrackerHitZCylinderImpl
with size of covariance matrix being 0 (no set to 6)
that caused corrupted LCIO files when any hits of these types
where written as "TrackerHit" types, e.g. in a new subset collection
that is made persistent ...
this is no problem for the DBD standard reconstruction !